Coaxial speed reducing gear set



M 1955 1... MACKTA COAXIAL SPEED REDUCING GEAR SET 2 Sheets-Sheet 3.

Filed Oct. 21, 1955 5/ E fiu fl U 1 f9 3 fl H 9 any M 5/ f. Z J y? 6% INVENTOR.

Mao MAJ www- IW W4 AT TQJW/VE Y IN VEN TOR. A A a MACKTA w L r I m. v.4 AY

Sept, 25, 1956 Filed Oct. 21, 1955 ATTORNEY u m M .l r

COAXIAL SPEED REDUCING GEAR SET Leo Mackta, Brooklyn, N. Y.

Application Gctober 21, 1955, Serial No. 542,053

7 Claims. (Cl. 74-2163) This invention relates to gear reducing devices, and more particularly to a gear reducing assembly of the type employing a worm driving gear element.

A main object of the invention is to provide a novel and improved gear reducing assembly which is simple in construction, which is compact in size, and which provides positive drive on a driven element substantially coaxial with the driving element of the assembly.

A further object of the invention is to provide an improved coaxial gear reducing assembly of the type employing a worm driving element and a driven element arranged coaxially with said driving element, the assembly being relatively inexpensive to fabricate, being durable in construction, and being of a type suitable for use for any one of a wide range of speed reduction ratios.

A still further object of the invention is to provide an improved coaxial gear reduction assembly which is positive in action, which involves a minimum number of parts, and which requires a minimum of lubrication.

Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawings, wherein:

Figure 1 is a longitudinal vertical cross-sectional view taken through a coaxial gear reducing assembly constructed in accordance with the present invention, taken on line 1-1 of Figure 2.

Figure 2 is a transverse vertical cross-sectional view taken on the line 2-2 of Figure 1.

Figure 3 is a fragmentary longitudinal vertical crosssectional view of the structure of Figures 1 and 2, showing fragmentary portions of the driving worm and ball race in elevational view, as employed in said structure, and showing a portion of the ball race in longitudinal vertical cross-section.

Figure 4 is a fragmentary longitudinal cross-sectional view of the driven member of the gear reducing assembly of Figures 1 to 3.

Figure 5 is a fragmentary longitudinal vertical crosssectional view taken through a modified form of coaxial gear reducing assembly according to the present invention, wherein the driving and driven elements are in the form of flat spiral gears.

Figure 6 is a fragmentary vertical cross-sectional view taken on the line 6-6 of Figure 5.

Figure 7 is a fragmentary longitudinal vertical crosssectional view taken through the ball race and driven element of a still further modified form of coaxial gear reducing assembly according to this invention, wherein spiral guide slots are provided in the ball race, and the driven element is provided with longitudinally extending ball grooves.

Referring to the drawings, and more particularly to Figures 1 to 4, one form of the improved gear reducing assembly of the present invention is designated generally at 11. The assembly 11 comprises a stationary support 12 in which is journalled a driving shaft 13. Integrally formed on shaft 13, or otherwise rigidly secured thereon, is a driving element comprising aworm 14 having a face 2 formed with a pair of spiral ball grooves 15, 15 and being formed with a pair of diametrically opposed internal ball passages 16, 16, connecting the ends of the respective ball grooves 15.

As shown in Figures 1 and 3, the worm 14 is tapered in diameter at its opposite end portions, as designated at 17, 17, and the respective ends of the ball grooves 15 communicate with respective spiral grooves 18 (Figure 2) formed in the end faces of the worm, said spiral grooves 18 leading to the respective ends of the internal ball passages 16.

Designated at 19 is a generally cylindrical ball race member which is secured at one end thereof to the support 12, as shown at 20, in coaxial relationship with worm 14. The ball race member is provided with an annular first end wall 21 surrounding shaft 13 and located adjacent support 12, and with a circular second end wall 22 located adjacent the outer end face of the worm 14. Member 19 is formed with a plurality of evenly spaced longitudinal ball race slots 23 extending longitudinally over the major portions of the ball grooves of worm 14 and terminating respective short distances inwardly of the end faces of the worm.

The race end walls 21 and 22 are respectively formed with annular inwardly facing, smoothly curved ball guide surfaces 24 and 25 extending toward the recesses 18 in the end faces of worm 14, and being formed to guide balls 26 from the ends of slits 23 into the recesses 13 at one end face of the worm and from the recesses 18 into slots 23 at the opposite end face of the worm responsive to rotation of the worm, as will be presently explained.

Designated at 27 is a substantially cylindrical, sleevelike driven member which receives the previously described worm and ball race assembly and which is in axial alignment therewith. Driven member 27 is provided with the end wall 28, and integrally formed with, or otherwise rigidly secured to said end wall, axially of the member 27, is the driven shaft 29, which is, of course, in axial alignment with the driving shaft 13. A thrust bearing ball 30 is engaged in opposing central recesses formed in race wall 22 and end wall 28 to define a thrust bearing between driven member 27 and the stationary race member 19.

The sleeve-like driven member 27 is formed with in ternal spiral ball grooves 31 of substantially different pitch than the worm grooves 15, in accordance with the amount of speed reduction required. The internal grooves 31 are spaced to receive the balls 26 therein, whereby torque may be transmitted to driven member 27 responsive to rotation of the driving worm 14. The end portions of the internal grooves are contoured to follow the contour of the tapered end portions of worm 1 5, as shown at 32, and the ends of the slots 23 are similarly contoured, so that balls 26 will travel smoothly toward and from the annular race guide surfaces 24 and 25 responsive to the rotation of the driving worm 14.

As shown, the balls 26 are inter-engaged with grooves 15 and 31 while being guided for longitudinal movernent by the longitudinal race slots 23. As each ball reaches the end of a slot 23, it is moved past the com toured end of the slot onto the end of the worm and is guided by the annular guide surface of the adjacent end.

Wall of the race into a spiral recess 18, and is then moved into a ball passage 16. Thus, assuming counterclockwise rotation of worm 14, as viewed in Figure 2, the balls are guided by the smoothly curved annular surface 24 into the recesses 18 and move through the passages in in a direction toward end wall 22 of the race member. Upon reaching end wall 22, the balls move outwardly through the spiral recesses 18 at the outer end face of worm 14 and are guided by the annular surface 25 of end wall 22 into the adjacent ends of the race slots 23.

Since the pitch of "the worm grooves 15 is different ---from-that-of theinternal grooves '31'of member -27, and

since the balls 26 are constrained to move longitudinally, torque is transmitted by the balls to the driven member 2:7, causing the driven isha'ft-29 to rotate at a speed re- :ductionwithwesp'ect to '-the driving shaft depending on-the di iferenceinpitch. By'ma-kingthe pitch of worm grooves 15 relatively small and that of internal grooves .31 relatively large, a large speed reduction can be obtained, without requiring the use or bulky additional gearing.

The-balls circulate continuously through the passages 16, thus-presenting continuously changing torque-trans mitti-ng elements between the driving and driven members, and minimizing the need for lubrication of the assembly.

-Although the worm member -14, race member 19, and sleeve member 27 ill-ustrated in Figures 1 to 4 are shown as being generally cylindrical in shape, said members may be conical in shape, within the 3spirt of the present invention, for example, may taper in diameter from the driving shaft 13toward theend wall 28 of the driven member 27, in which case the torque-transmitting balls 26 may be utilized as thrust bearing members 'in place of the thrust bearing ball '30. As a limiting case of such a variation'in the angle of taper of these members, Figures 5 and 6 illustrate an embodiment of the invention wherein the driving member, shown at 14, is in the form of acircular body secured on the driving shaft 13' and being formed on its front transverse face with spiral driving grooves 15. The driving member 14' is formed with a pair of diametrically opposed, substantially radial internal passages 16' communicating at their ends with annularly recessed portions 40 and 41 formed in member 14 respectively at the peripheral and at the inner ends of the spiral grooves in the face of said member 14'.

The driving gear 14 is received in a circular recess 42 formed in a suitable support 12 in which shaft 13 is journalled. Secured to said support 'at the rim of said recess and extending adjacent the spirally grooved face of gear 14 is the race plate 1'9, said plate 19' being formed with a plurality ,of radial slots 23' crossing the spiral grooves 15' and terminating adjacent the peripheral and inner ends of said spiral grooves. The race plate 19' is formed adjacent the inner and outer ends of the slots 23 with annular thickened portions and 44 formed with respective smoothly curved annular guide surfaces 45 and 46 directed toward and leading to the opposite ends of the internal ball passages in.

The jdriven member of the assembly shown in Figures 5 and -6 comprises a circular gear 27' mounted on the driven shaft 2.9, which is journalled in 'a suitable support 47 and which is in coaxial alignment with driving shaft 13. As shown, gear 27' is located closely 'adjacent to race plate 19 and is formed with spiral grooves '31 in its face of substantially different pitch than the spiral grooves 15' of the. drivinggear.

The torque-transmitting balls, shown at 26, are guided radially through the race slots '23, being driven "by the rotation of driving gear 14' and by the action of the spiral grooves 15. Torque is transmitted by the balls 26 to the driven gear 27 by the action of the balls against the walls of the spiral grooves 31. When the balls reach the ends of the radial slots 23', they are moved into engagement with the adjacent thickened annular guide .portion 43 or 44 of the race plate and are moved against the adjacent recessed inner or outer portion 41 or 40 of the driving gear and are guided into the adjacent ends of the internal ball passage 16. Thus, assuming the direction of rotation of driving gear .13 to be such that ,balls 26' are :rnoved in slots 23 away from theaxis of the assembly, when the balls reach the outer ends of vsaid slots theyvengage guide surface .46 and are moved toward recessed portion 40. .Saidballs are guided in sequence by surface 46 into the outer ends of the through said passage 4 passages 16, and are progressively moved inwardly 'At "the inner ends of passages 16, the balls engage annular guide surface 45 and are guided sequentially into the inner ends of the radial slots 23'.

it will be understood that basically only one internal ball passage 16 or 16 is required, but that in the above described forms of the iuvrerition it is preferable to em ploy at least two diametrically opposed internal ball passages "for proper mechanicalbalan'ce, and two parallel spiral grooves-on :the driving face.

instead of employing spiral grooves in the face of the driven member, the race member may be -formed with spiral ball slots andstheifacebf thedriven member may be provided with straight ball grooves. Thus, in the modification of the assembly illustrated in Figure 7, the stationary race member, designated at St), is formed with thespiral ball slots 51, and the driven sleeve member, designated at '52, is formed on its inside'face with the straight, longitudinally extending ball grooves 53, serving to guide the torque-transmitting balls 26 in spiral paths along the racemember :responsive to rotation of the driving worm. The spirally moving balls 26 act against the walls of the longitudinal grooves 53 of the driven member 52 to apply torque to said driven memher, and to rotate :the idriv'e'n shaft, shown at '54, at a speed reduction in accordance with 'the difference in pitch between the spiral grooves Jon the driving worm and the spiral slots 51.0f .race member 59.

While certain "specific embodiments of an improved coaxial gear reducing assembly have been disclosed in the foregoing description, it will be understood that various modifications within the spirit of the invention may occur to 'thoseskilled in theart. Therefore it is intended that no limitations 'be'placed on the invention except as defined by the :scope of the appendedclaims.

What is claimed ,is:

1. -A:g'e,ar reducing assembly comprising a driving element, spiral ball "guide means on said driving element, said driving element being formedwith an .internal ball passage communicating with "the opposite ends of said spiral "ball guide means, a stationary race membersccured adjacent said driving element and extending adjacent and over the face of said driving element, said race member being formed with a ball guide slot crossing said ball guide means and being formed and arranged .to define a ball passage 'connectingthe opposite ends of said spiral .ball guide means, a driven element coaxial with said driving element, said .fdriven element having a face portion extending adjacent said race member, said face portion being formed with ball guide grooves .registrable with the superimposed portions of the ball guide slot and the ball guide means, and a plurality of ball members in .said raceba'll passage engaged in said superimposed portions and ball guide grooves and disposed in said internal ball passage.

2. A gear reducing assembly-comprising-a .driving'element, said driving element being formed-with :aspiral ball groove and being formed with an internal ball passage communicating with :the opposite ends of said spiral groove, a stationary race member secured adjacent said driving element andextending adjacent and over "the face of said driving element, said race member being formed witha ball guide slot'cross'ingsaid ball groove and being formed and arranged to define "a 'ballpassage connecting the opposite ends of said spiralba'll groove, a driven element coaxial with said driving element, said driven relementhaying a face portion extending adjacent said race member, .said face portion being formed with ball guide grooves ,registrable with the Superimposed portions of the ballguide slot and the -first-named spiral vballgroove, and ,a plurality of ball .membcrsin said race :ball passage engagedin said driving and driven element ball grooves and disposed .in ,saidinternal ball passage.

3. The structure of claim 1, and wherein said driving element is tapered in thickness at the opposite end portions of the spiral ball guide means and the race member is formed with smoothly curved guide surfaces at the opposite ends of the guide slot directed toward the ends of the internal ball passage in the driving element.

4. The structure of claim 2, and wherein said driving element is tapered in thickness at the opposite end portions of the spiral ball groove therein and the race memher is formed with smoothly curved guide surfaces at the opposite ends of the guide slot directed toward the ends of the internal ball passage in the driving element.

5. A speed reducing gear set comprising a support, a driving element journalled in said support, said driving element having a face formed with a spiral ball groove and being formed with an internal ball passage connecting the ends of said spiral ball groove, a race member secured to the support and extending over the grooved face of the driving element, said race member being formed with a ball guide slot extending across the spiral ball groove from one end of the grooved face portion of the driving element to the other, a driven element having a grooved face disposed adjacent the race member and extending substantially from one end of the spirally grooved face portion of the driving element to the other, means rotatably supporting the driven element in coaxially aligned relation with the driving element, a plurality of balls disposed in the grooves of the driving and driven elements and in the ball guide slot, said balls being disposed in the internal ball passage, and means guiding said balls from one end of the race slot into the internal ball passage and from the ball passage into the other end of the race slot responsive to rotation of said driving member.

6. A speed reducing gear set comprising a support, a driving element journalled in said support, said driving element having a face formed with a spiral ball groove and being formed with an internal ball passage connecting the ends of said spiral ball groove, a race member secured to the support and extending over the grooved face of the driving element, said race member being formed with a ball guide slot extending across the spiral ball groove from one end of the grooved face portion of the driving element to the other, a driven element having a grooved face disposed adjacent the race member and extending substantially from one end of the spirally grooved face portion of the driving element to the other, the grooves in the driven element having a pitch substantially different from that of the grooves in the driving element, means rotatably supporting the driven element in coaxial aligned relation with the driving element, a plurality of balls disposed in the grooves of the driving and driven elements and in the ball guide slot, said balls being disposed in the internal ball passage, and means guiding said balls from one end of the race slot into the internal ball passage and from the ball passage into the other end of the race slot responsive to rotation of said driving member.

7. A speed reducing gear set comprising a support, a driving element journalled in said support, said driving element having a face formed with a spiral ball groove and being formed with an internal ball passage connecting the ends of said spiral ball groove, a race member secured to the support and extending over the grooved face of the driving element, said race member being formed with a ball guide slot extending across the spiral ball groove from one end of the grooved face portion of the driving element to the other, a driven element having a grooved face disposed adjacent the race member and extending substantially from one end of the spirally grooved face portion of the driving element to the other, means rotatably supporting the driven element in coaxial aligned relation with the driving element, and a plurality of balls disposed in the grooves of the driving and driven elements and in the ball guide slot, said balls being disposed in the internal ball passage, the driving element being recessed at the ends of the spiral groove therein to define guide passages connecting the ends of its spiral ball groove to the ends of the internal ball passage therein, and the race member being formed with annular ball guide surfaces extending toward the recessed ends of the driving element.

No reference cited, 

